I just spent the last two nights reading this whole thread. Very entertaining and informative. The whole time however, I wanted to ask about your bore job for the OS1 pistons you were using. I too used OS1 Mahles and have been very unhappy with the results, namely, I feel my machine shop didn't bore round holes or used bad specs. I hope you will monitor the results before you assemble the new block. I feel much of my timing pull issues are related to piston slap and I wonder if that hasn't been problem for you in getting the tune set up. I also imagine your excessive blow by might be a result of the same problem. I am no machinist but without some way to keep the free standing bores in line during the bore work, you end up with odd shaped bores. If you are going to weld/block the tops of the cylinders, do it before the machine work.
I have had three different machine shops do head work and each of them have ruined several valve seals by mashing them to oblivion. I have redone plenty of seals.
I have been trying to find a flange for my TD05 20G, like yours with the welded wastegate plug, but have had no success. In looking at your latest pics, it appears that you used the TD06 flange and slotted the holes. Is that correct? I want to unplug the wastegate and run a divorced setup as well, may have to fab flange.
I have an 01 LPT motor waiting to go in the R and because of my machine shop jitters, I am going to put it in without a teardown. If that fails, I will grab a 2.3 block and use my already balanced/forged/OS1 bottom end and move on.
I am excited to use the LPT motor since 98% of my driving is at 4200 ft. I feel the slightly higher CR will be less "soft" off idle.
I am very interested in your intake and am considering using the RN intake runners to create something like yours. I enjoy watching your process of need/design/build. hats off to you for boldly going etc.
Finally, I haven't driven an X/19 in years but I envy you yours!